The invention relates to a valve construction wherein solenoid excitation of an elongate magnetostrictive core element is relied upon to actuate a valve for control of a fluid flow, as for controlling the flow of a pressure fluid from an upstream source to an outlet for downstream storage or utilization at reduced pressure. The invention has illustrative application as a regulating valve, wherein the upstream supply pressure is, at least initially, in the order of 2000 psia, and wherein a relatively small-volume tank (e.g., a 6-inch length of tubing of 0.22 inch ID) is to be loaded with ramped increasing pressure to a set point of outlet pressure in the order of 27 psia, the valve being automatically modulated as needed to maintain tank ullage pressure in an operating band of .+-.1.5 psi, during step on-off demands for operating fluid from the tank.
For the kind of spacecraft application which favors the invention, the valve is necessarily of normally closed variety and a very high seating force is desired to provide positive sealing and very low leakage under lock-up (i.e., valve-closed) conditions. Pressurized propellant gas for maneuvering must be conserved at all costs, relying upon valves with superior (i.e., very low) leakage resistance under lock-up conditions, yet offering fast response to instant demand. Thus, shut-off, isolation, low friction, mechanical simplicity and small size are important considerations in a valve of the character indicated. A magnetically latching and magnetically actuated valve of the nature described in U.S. Pat. No. 3,814,376 or in pending application Ser. No. 08/184,484 has properties approaching the desired low-leakage of a valve-closed condition, but the time constant for valve actuation (opening or closing) is greater than would be desired, and the seating force is less than desired.